An organic light-emitting element is an electronic element including an anode and a cathode, and an organic compound layer placed between both the electrodes. A hole and an electron injected from the respective electrodes (the anode and the cathode) recombine in the organic compound layer to produce an exciton, and the organic light-emitting element emits light upon relaxation of the exciton to its ground state. Recent development of the organic light-emitting elements is significant and the developed elements have, for example, the following features. The light-emitting elements can be driven at low voltages, emit light beams having various wavelengths, have high-speed responsiveness, and can be reduced in thickness and weight.
Of the organic light-emitting elements, a phosphorescent light-emitting element utilizing phosphorescence is a light-emitting element that includes a phosphorescent light-emitting material in its organic compound layer and excites the phosphorescent light-emitting material to provide light emission derived from a triplet exciton. However, the phosphorescent light-emitting element has room for additional improvements from the viewpoints of its luminous efficiency and durability lifetime. Specifically, an improvement in emission quantum yield of the phosphorescent light-emitting material and suppression of deterioration of a molecular structure of a host molecule in a light-emitting layer have been main problems.
An iridium complex having a red light-emitting arylbenzo[f]isoquinoline as a ligand (hereinafter described as a biq-based Ir complex) has been known as one phosphorescent light-emitting material having a high emission quantum yield. Patent Literature 1 discloses an organic light-emitting element whose light-emitting layer contains Ir(pbiq)3 (biq-based Ir complex) represented by the following formula as a guest and CBP as a host for an improvement in luminous efficiency.

In addition, Patent Literature 2 discloses an organic light-emitting element whose light-emitting layer contains, as a host, a benzo-fused thiophene or benzo-fused furan compound that is a heterocycle-containing compound.